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# payments.simulate

> Run the full policy envelope evaluation against a proposed payment. Returns the verdict + every reason without any side effects. Use this to preview a payment b

Run the full policy envelope evaluation against a proposed payment. Returns the verdict + every reason without any side effects. Use this to preview a payment before calling payments.initiate.

## Metadata

| Field                    | Value               |
| ------------------------ | ------------------- |
| Name                     | `payments.simulate` |
| Category                 | `read`              |
| Required scope           | `payments:simulate` |
| Idempotency key required | no                  |

## Annotations

| Annotation              | Value            |
| ----------------------- | ---------------- |
| Title                   | Simulate Payment |
| Read-only               | yes              |
| Destructive             | no               |
| Idempotent              | yes              |
| Open-world              | no               |
| Requires human approval | no               |

## Input schema

```json theme={null}
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "counterparty": {
      "type": "object",
      "properties": {
        "address": {
          "type": "string",
          "minLength": 1
        },
        "chain": {
          "type": "string",
          "enum": [
            "eth",
            "base",
            "arb",
            "op",
            "polygon",
            "sol"
          ]
        },
        "token": {
          "type": "string",
          "minLength": 1
        }
      },
      "required": [
        "address",
        "chain",
        "token"
      ],
      "additionalProperties": false
    },
    "amount_cents": {
      "type": "integer",
      "minimum": 0,
      "maximum": 9007199254740991
    },
    "currency": {
      "type": "string",
      "minLength": 1,
      "maxLength": 8
    },
    "mcc": {
      "type": "string",
      "minLength": 4,
      "maxLength": 4
    },
    "geo": {
      "type": "string",
      "minLength": 2,
      "maxLength": 2
    }
  },
  "required": [
    "counterparty",
    "amount_cents",
    "currency"
  ],
  "additionalProperties": false
}
```

## Output schema

```json theme={null}
{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "verdict": {
      "type": "string",
      "enum": [
        "allow",
        "allow_with_step_up",
        "deny"
      ]
    },
    "policy_version": {
      "type": "integer",
      "minimum": 0,
      "maximum": 9007199254740991
    },
    "reasons": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "axis": {
            "type": "string"
          },
          "reason_id": {
            "type": "string"
          },
          "message": {
            "type": "string"
          }
        },
        "required": [
          "axis",
          "reason_id",
          "message"
        ],
        "additionalProperties": false
      }
    },
    "simulated_at": {
      "type": "string",
      "format": "date-time",
      "pattern": "^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))T(?:(?:[01]\\d|2[0-3]):[0-5]\\d(?::[0-5]\\d(?:\\.\\d+)?)?(?:Z))$"
    }
  },
  "required": [
    "verdict",
    "policy_version",
    "reasons",
    "simulated_at"
  ],
  "additionalProperties": false
}
```

## Auth

Caller's grant must include the `payments:simulate` scope. Grants whose scope set is a superset of the required scope are accepted.

## Request examples

<CodeGroup>
  ```bash curl theme={null}
  curl -X POST https://mcp.glide.co/mcp/read \
    -H "Authorization: Bearer $GLIDE_GRANT_TOKEN" \
    -H "Content-Type: application/json" \
    -d '{
      "jsonrpc": "2.0",
      "id": 1,
      "method": "payments.simulate",
      "params": {
        "counterparty": {
          "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
          "chain": "base",
          "token": "USDC"
        },
        "amount_cents": 75000,
        "currency": "USD",
        "mcc": "7372"
      }
    }'
  ```

  ```ts TypeScript theme={null}
  import { GlideClient } from './glide-client';

  const client = new GlideClient({ grantToken: process.env.GLIDE_GRANT_TOKEN! });

  const result = await client.call('payments.simulate', {
    counterparty: {
      address: '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045',
      chain: 'base',
      token: 'USDC',
    },
    amount_cents: 75000,
    currency: 'USD',
    mcc: '7372',
  });

  if (result.verdict === 'deny') {
    console.error('Payment would be denied:', result.reasons);
  } else if (result.verdict === 'allow_with_step_up') {
    console.log('Payment requires step-up before initiating');
  } else {
    console.log('Payment would be allowed — safe to call payments.initiate');
  }
  ```

  ```python Python theme={null}
  from glide_client import GlideClient
  import os

  client = GlideClient(grant_token=os.environ["GLIDE_GRANT_TOKEN"])

  result = client.call("payments.simulate", {
      "counterparty": {
          "address": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
          "chain": "base",
          "token": "USDC",
      },
      "amount_cents": 75000,
      "currency": "USD",
      "mcc": "7372",
  })

  print(result["verdict"], result["reasons"])
  ```
</CodeGroup>

## Response examples

Verdict — allowed:

```json theme={null}
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "verdict": "allow",
    "policy_version": 3,
    "reasons": [],
    "simulated_at": "2026-05-04T12:00:00Z"
  }
}
```

Verdict — step-up required (amount above threshold, otherwise allowed):

```json theme={null}
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "verdict": "allow_with_step_up",
    "policy_version": 3,
    "reasons": [
      {
        "axis": "amount",
        "reason_id": "step_up_threshold",
        "message": "amount 750000 exceeds step_up_amount_cents 100000"
      }
    ],
    "simulated_at": "2026-05-04T12:00:00Z"
  }
}
```

Verdict — denied (daily cap would be breached):

```json theme={null}
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "verdict": "deny",
    "policy_version": 3,
    "reasons": [
      {
        "axis": "velocity",
        "reason_id": "daily_cap_exceeded",
        "message": "daily spend cap of 100000 cents would be exceeded; current spend 90000"
      }
    ],
    "simulated_at": "2026-05-04T12:00:00Z"
  }
}
```

## Errors

| Code     | Name            | Cause                                                                           | Remediation                                      |
| -------- | --------------- | ------------------------------------------------------------------------------- | ------------------------------------------------ |
| `-32600` | Invalid request | Malformed JSON-RPC envelope                                                     | Check `method`, `jsonrpc`, and `id` fields       |
| `-32602` | Invalid params  | `counterparty.chain` not in enum, `currency` empty, or MCC not exactly 4 digits | Validate against the input schema before calling |
| `-32001` | Unauthorized    | Missing/expired grant token                                                     | Refresh via `agent.grant.refresh`                |
| `-32002` | Policy denied   | Grant missing `payments:simulate` scope                                         | Issue a new grant with the required scope        |
| `-32603` | Internal error  | Envelope or velocity-context fetch failed                                       | Retry — simulate has no side effects             |